Raechal
Fish Gatherer
Go to walmart in the garden section and pick up a bag of playsand. It is used to sandboxes and stuff like that. It is like $1.67 a bag and the bag is like 40 pounds I think. But the sand looks a lot smaller in the water once it is all compacted down so maybe get 2 bags for your 20 gallon.
Then you can get maybe some rocks or wood at the LFS.
Then you can get maybe some rocks or wood at the LFS.